The present invention relates generally to vehicle steering and suspension systems and, in particular, to a joint for use in a strut-type vehicle steering and suspension system.
Many automotive vehicles today employ a type of front suspension commonly known as a McPherson strut suspension. This type of suspension includes a strut assembly, with an upper strut mount affixed to a vehicle frame or body and a lower end affixed to a steering knuckle. The lower end of the steering knuckle also attaches, via a conventional ball joint, to a lower control arm, which is hinged to the vehicle frame or body. While this conventional suspension works well for many vehicle applications, it creates a spindle length—the distance from the wheel center plane to steer axis along the wheel rotation axis—that is larger than desirable. The steer axis is located away from the wheel center plane due to the fact that, with this suspension, it is defined by the ball joint and upper strut mount location. This large spindle axis undesirably increases steering system loads when tractive forces (front wheel drive), road profile impact forces, or rotating assembly imbalance forces are applied. This undesirable increase in steering system loads is particularly noticeable on front wheel drive vehicles with high-powered engines. On these types of vehicles, traction steer concerns may become apparent during combined acceleration and turn events.
While a different type of suspension may be provided for such high-powered vehicles, this may require substantial changes to the vehicle's frame or body to accommodate this different suspension. The cost to make these changes on an existing vehicle may be prohibitive, leaving one only the choice of the conventional suspension. Consequently, it is desirable to improve the suspension and steering performance on vehicles where the frame or body has already been designed specifically for a McPherson strut suspension without having to substantially modify the frame or body of that vehicle, and while remaining generally within the packaging space of the conventional McPherson strut suspension. Moreover, it is desirable to provide these improvements while also assuring that the fabrication and assembly of the components is relatively straight forward and easy, and while minimizing a need for special tools during assembly.